EMD SD-series frame reference

[trainiac]

While on the subject of SD35's, are the former NW ones now on MRL rebuilt with 16 cylinder 645's?

I don't think so. A roster I've found lists them as 2500 hp, and they still have turbocharger stacks. The 35-units that I'm aware of that were modified with 645 power assemblies were derated to 2000 hp in the process (with the turbo removed).

[Allen Hazen]

Michael Eby--
(More a thinking-out-loud and wondering post than anything else....)
645 power assemblies and de-turbo-ing with a 2000 hp rating are one way of dealing with high-maintenance EMDs from the early 1960s: I think Penn Central started it with ex-NYC GP20, but there are also turbocharged rebuilds.
I **think** ATSF rebuilt a large number of GP30/GP35 with turbochargers, 645 power assemblies, alternators, and a rating of 2500 or 2600 hp. And I've never gotten straight as to just WHAT went into a BN "GP39V" or "GP39E".
(Which, since the string was about SD units, is pretty far off topic. Sorry!)

[es80ac]

Anybody know for sure if SD90 frames are actually thicker than the SD70 and all the previous SDs? Or is it just SD90 body sits higher on the frame, and expose more of it? Not sure what the practical reason is, but seems like EMD just want to have their diesel sit at least as tall as the modern GE. Previously Dash 8 and Dash 9 towers somewhat over the EMD counter parts.

[Allen Hazen]

Does the FRA have a safety rule about the walkways of all locomotives being the same height? I have a vague recollection that in the 1950s they (or some predecessor agency) had vaguely-worded standards about steps in walkways, different interpretations of which led to variations in FM Trainmaster design...

[trainiac]

Anybody know for sure if SD90 frames are actually thicker than the SD70 and all the previous SDs? Or is it just SD90 body sits higher on the frame, and expose more of it? Not sure what the practical reason is, but seems like EMD just want to have their diesel sit at least as tall as the modern GE. Previously Dash 8 and Dash 9 towers somewhat over the EMD counter parts.

They are thicker. EMD's frames have thickened gradually (to compensate for the length increases) so that it's no overly obvious from one model to the next. But put an early GP35 next to an SD40-2 and, even then, the difference is obvious.

The walkway height on the SD90MAC is almost 4 inches higher than an SD70, but similar trucks are used. The only other reason for the increase I can think of would be an additional 1.5" from the larger wheels--but that doesn't account for the entire height increase. The overall height of the SD90MAC isn't that much more than the SD70 series, because the fans and hood don't extend much higher than the cab roof.

Interestingly, GE has gone in the opposite direction. The frame height of late six-axle Dash-8's and Dash-9's is substantially lower (something like 4 or 5 inches) than their earlier six-axle units. The change occured in the switch from the C40-8 to the C40-8W. The result is that the frame of an SD70ACe (which is thick, like the SD90MAC) is now several inches above the frame of a GEVO, while it used to be that the frame of a Dash-7 or early Dash-8 towered far above almost anything EMD had to offer.